JPH0536160Y2 - - Google Patents

Description

[Detailed explanation of the invention] [Field of industrial application] This invention is a liquid inflow system that prevents liquid from getting mixed into the gas line for recovering gas generated in low-temperature liquefied gas liquid lines and liquid storage tanks. Regarding prevention equipment, it is suitable for installation in the receiving piping, gas line, etc. between the LNG tank and the LNG ship.

[Conventional technology]

Gas generated in liquid lines and liquid storage tanks for low-temperature liquefied gases such as LNG (liquefied natural gas) may increase pressure within the system and cause difficulties in pumping, so it may be necessary to collect and process the gas. many.

For example, in LNG tank 1 as shown in Figure 2,
Reception line 3 that receives LNG from LNG carrier 2
A large number of gas vent sections 4 (only one is shown in the illustrated example) are provided in the LNG tank 1 in order to recover the gas generated in the line and at the same time maintain a constant pressure in the hold of the LNG carrier 2. Gas corresponding to the amount received is returned through the gas line 5, and gas in the receiving line 3 is also returned using the gas line 5.

In such a gas line 5, if liquid enters the system, gas cannot be supplied to the LNG carrier 2,
Negative pressure occurs in the hold, reducing unloading speed,
Unloading operations would have to be suspended.

Also, if a large amount of liquid gets mixed into the gas line 5,
Liquid also enters the gas supply blower (not shown), causing damage to seals and other parts that are not necessarily designed for low temperatures.

Therefore, in order to prevent liquid from entering the gas line 5 from the liquid line (receiving line 3), for example, as shown in FIG. A pot 9 is provided in addition to which valve 7 or the level adjustment valve 8 is installed, and the level adjustment valve 8 is adjusted by a signal from the level sensor 10 installed in the gas vent section 4.
It opens and closes to adjust the liquid level to prevent liquid from getting mixed in, and also detects the temperature of the gas vent section 4 with a temperature sensor 11 and opens and closes the shutoff valve 7 to prevent liquid from getting mixed in. A temperature sensor 12 detects the temperature change due to the amount of liquid stored in the pot 9 and issues an alarm.

[Problem to be solved by the invention] However, in such equipment for preventing liquid from entering the gas line 5, the liquid level in the gas venting section 4 may be reduced, such as in a transient state where the pressure in the liquid line 3 is changing. If the value drops momentarily, the shutoff valve 7 and level adjustment valve 8
However, when the LNG carrier 2 is unloaded in a fully open state, the degassing section 4 is filled with liquid. If the operator sometimes forgets to close the valve, there is a problem that a large amount of liquid may get mixed in.

This invention was made in view of the problems of the prior art, and is intended to provide equipment for preventing liquid from flowing into the gas line, which can prevent liquid from entering the gas line.

[Means to solve the problem]

In order to solve the problems of the above-mentioned conventional technology, the device for preventing liquid from flowing into the gas line of this invention has a cutoff valve interposed in the gas vent line that communicates the gas line with the gas vent section provided in the liquid line. On the other hand, temperature detectors are installed above and below the gas line, and a controller is provided that closes the shutoff valve when the temperature difference between the upper and lower sides and the rate of temperature change detected by the upper and lower temperature detectors exceed a set value. This is a characteristic feature.

[Effect]

Temperature sensors are installed above and below on the gas line side, and the temperature difference and temperature change rate are determined from the detection signals from the upper and lower temperature sensors.If both of these exceed the set value, a signal from the controller is sent to The shutoff valve on the vent line is closed, and liquid contamination is monitored on the gas line side.By adding this to the detection of liquid in the liquid line and gas vent line, further safety is ensured.

〔Example〕

Hereinafter, one embodiment of this invention will be described in detail based on the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment of the device for preventing liquid inflow into a gas line of this invention, when applied to an LNG receiving line.

In this equipment 20 for preventing liquid from flowing into the gas line,
By detecting the level and temperature in the degassing section 4 on the side of the receiving line 3 or the temperature of the pot 9, which have already been explained based on FIG. In addition to preventing liquid from entering the gas line 5 via the gas vent line 6, the state within the gas line 5 is also detected to prevent liquid from entering.

For this reason, temperature detectors 21 and 22 are installed at the upper and lower ends of the gas line 5, respectively, and the temperature is inputted to the controller 23.

In addition, the gas vent line 6 includes a cutoff valve 7, a level adjustment valve 8, and front and rear manual valves, as well as a cutoff valve 24.
is interposed between the front and rear manual valves, and is opened and closed in response to a control signal from the controller 23.

The controller 23 that opens and closes the shutoff valve 24 calculates the temperature difference dT between the upper and lower sides of the gas line 5 from the detected values of the temperature sensors 21 and 22 attached to the upper and lower sides of the gas line 5, and also calculates the temperature change rate dT/dt. A closing signal is output to the cutoff valve 24 when both the temperature difference dT and the rate of change dT/dt exceed set values.

These set values for temperature difference dT and rate of change dT/dt are set as values corresponding to a state where a considerable amount of liquid is mixed in, since even a small amount of liquid mixed in the gas line 5 does not cause a big problem. In the case of an LNG receiving line, the temperature difference dT is 15℃, and the rate of change dT/
dt is set in the range of 10℃/min.

In the equipment 20 for preventing liquid from flowing into the gas line configured in this way, the shutoff valve 7 and the level adjustment valve are normally controlled depending on the liquid level and temperature in the gas venting section 4 using the level sensor 10 and temperature sensors 11 and 12. 8, and an alarm is issued depending on the liquid level in the pot 9 to prevent liquid from entering the gas line 5.

However, if liquid gets mixed into the gas line 5 through the gas vent line 6 for some reason, the temperatures detected by the temperature sensors 21 and 22 installed above and below the gas line 5 will change. They differ greatly, and if the temperature difference becomes large or the amount of liquid increases, the temperatures will become almost the same.

At the same time as this temperature difference dT, the rate of temperature change dT/dt is calculated, and since the rate of temperature decrease increases due to the contamination of liquid, and the rate of temperature decrease is small due to the contamination of a small amount of liquid, the rate of temperature change dT / dt is determined. When the amount is detected and these two conditions are satisfied at the same time, it is determined that a considerable amount of liquid has mixed in, and the controller 23 outputs a closing signal to the shutoff valve 24 to prevent the inflow of liquid.

In this way, the liquid inflow prevention equipment 20 into the gas line
By providing this, it is possible to detect the amount of liquid that has entered the gas line 5 and prevent the liquid from entering, so that the inflow of liquid can be prevented more reliably.

In addition, if it is used together with the conventional liquid inflow prevention equipment on the receiving line 3 side as in this embodiment, it is possible to more reliably prevent liquid from entering.

In the above embodiment, the case where the present invention is applied to an LNG receiving line has been described, but the present invention is not limited to this and can be widely applied to other low-temperature liquefied gas lines, liquid storage tanks, and the like.

Furthermore, the setting values may be set appropriately for items other than LNG.

[Effect of idea]

As described above in detail with one embodiment, according to the equipment for preventing liquid from flowing into the gas line of this invention, the gas venting line that communicates the gas venting part provided in the liquid line with the gas line is blocked. In addition to installing a valve, temperature detectors are installed above and below the gas line, and a controller is provided that closes the shutoff valve when the temperature difference between the upper and lower sides and the rate of temperature change detected by the upper and lower temperature detectors are above a set value. Since this is provided, liquid contamination can be monitored on the gas line side, and in addition to liquid detection in the liquid line and gas vent line, liquid contamination can be more reliably prevented.

Furthermore, it is possible to detect situations such as transient states, which are difficult to handle with conventional equipment, and prevent liquid contamination.

[Brief explanation of the drawing]

Figure 1 shows an example of the equipment for preventing liquid from flowing into gas lines according to this invention, and is a schematic diagram when applied to an LNG receiving line. Figure 2 shows a conventional equipment for preventing liquid from flowing into gas lines. FIG. 2 is a schematic configuration diagram when applied to an LNG receiving line. 1... LNG tank, 2... LNG ship, 3... Receiving line, 4... Gas venting section, 5... Gas line, 6... Gas venting line, 7... Shutoff valve, 8...
... Level adjustment valve, 9 ... Pot, 10 ... Level sensor, 11, 12 ... Temperature sensor, 20 ... Equipment for preventing liquid from flowing into the gas line, 21, 22 ... Temperature sensor, 23 ... Controller, 24...Shutoff valve.

Claims (1)

[Scope of utility model registration request] A shutoff valve is installed in the gas vent line that communicates the gas vent with the gas vent provided in the liquid line, and temperature detectors are installed above and below the gas line, and the temperature detected by these upper and lower temperature detectors is 1. Equipment for preventing liquid from flowing into a gas line, characterized in that a controller is provided that closes the shutoff valve when the upper and lower temperature difference and the rate of temperature change are above a set value.